In New Zealand, agricultural activity accounts for the majority of greenhouse gas emissions. Therefore, reducing agricultural emissions of greenhouse gases is important for meeting New Zealand's obligations under the Kyoto Protocol. The Protocol requires reduction of greenhouse gases to 1990 levels by the end of the first commitment period (2008-2012). To this end, agricultural sector groups and the New Zealand government established the Pastoral Greenhouse Gas Research Consortium (PGGRC) to identify means for reducing New Zealand's agricultural greenhouse gas emissions.
An important part of the PGGRC's activities has been research into reducing methane emissions from New Zealand's grazing ruminants. Mitigating methane emissions from ruminants is of commercial interest for two reasons. First, failure to meet commitments under the Kyoto Protocol will force the government to purchase carbon credits. This is currently estimated to cost $350 million. Second, methane production results in the loss of 8-12% of the gross energy produced in the rumen. This energy could be used, instead, to improve ruminant productivity.
Methane is produced in the rumen by microbes called methanogens which are part of the phylum Euryarchaeota within the kingdom Archaea. Most methanogens grow on CO2 and H2 as their sole energy source, but some can use acetate or methyl compounds for growth. Several different genera of methanogenic archaea exist in the rumen, but species of the genus Methanobrevibacter, especially M. ruminantium, and M. smithii are thought to be the predominant methanogens in New Zealand ruminants. M. ruminantium is currently the subject of a genome sequencing project funded by the PGGRC. The project is the first genome sequencing of a rumen methanogen and it aims to build a better understanding of the biology of Methanobrevibacter to discover targets for inhibition of methane formation.
Reducing methane production in the rumen requires the inhibition of methanogens or the inactivation of their methanogenesis pathway. A means of inhibiting methane production is to deliver specific inhibitory molecules into methanogen cells. This may be achieved, for example, by use of agents, such as bacteriophage, which specifically target methanogens. Several phage have been characterised for non-rumen methanogens but there have been no published accounts of phage able to infect or lyse rumen methanogens. Therefore, it would be highly advantageous to identify phage that have the ability to infect methanogen cells and/or deliver inhibitors.